Dewar for liquid air and/or other multicomponent cryogenic liquids



' y 12, 1965 R. s. PAULIUKONIS ETAL" 3,250,050

DEWAR FOR LIQUID AIR AND/0R OTHER MULTICOMPONENT CRYOGENIC LIQUIDS Filed Aug. 26, 1964 INVENTORS RICHARD $.Pnuuuxoms G ORGE M now ATTORNEYS 3,260,060 DEWAR FOR LIQUID AIR AND/R OTHER MULTICOMPONENT CRYOGENIC LIQUIDS Richard S. Pauliukonis and George Matlow, Cleveland,

Ohio, assignors to Ryan Industries, Inc., Cleveland,

Ohio, a corporation of Ohio Filed Aug. 26, 1964, Ser. No. 394,099 3 Claims. (Cl. 62-45) This invention relates to cryogenic Dewar, and more particularly to an insulated storage vessel for housing multi-component mixtures such as, for example, liquid air of standard concentration of 79% N and 21% 0 The invention thus has application in the cryogenic field for storing liquefied gases with boiling points considerable below ambient air temperature requiring provisions for the control of consistency in concentration. In particular, this is important in storing standard liquefied air for an extended duration.

Cyrogenic storage vessels for other liquefied gases, such as monocomponent liquid oxygen, liquid nitrogen, liquid hydrogen, and other pure gases, are designed with insulated jackets to permit as little as possible heat flow into the liquid in order to prevent excess vaporization. Since it is physically impossible to completely eliminate heat leak into the stored liquid, the formation of vapor gradually raises the pressure in the vessel, which eventually would burst the container unless provided with vent valves and/or pressure relief devices. Automatic pressure relief devices normally are spring loaded safety relief valves and/or vent valves which reseat at some lower pressure after venting the accumulated excess vapor without adverse effect to the remaining liquid in the storage tank.

Liquid air, however, is a binary fluid composed of nitrogen and oxygen, and as such responds differently to the heat leak. Due to the dilfereuce of partial pressures more nitrogen vaporizes than oxygen and the resultant vapor composition is nitrogen rich; i.e., while liquid phase air at 30 p.s.i.a. is 71% mol N and 29% mol O vapor phase air is 92% mol N and 8% mol 0 It should be apparent from the above that if liquid air converted to vapor were allowed to escape through the safety relief valve, the remaining liquid would gradually become oxygen rich. Such change in composition of liquid air is undersirable from both safety and product consistency standpoints. To insure product consistency when storing multicomponent mixtures and/or binary fluids, such as liquid air, means, other than venting vapor, must be employed.

It is, therefore, an object of the present invention to provide a cryogenic vessel which entails such means and fulfills the requirements of storing binary, and/or m-u-lticomponent mixtures of cryogenic fluids such as liquid air, without venting more volatile vapor such as nitrogen-rich gas from the vapor space, more effectively than other current or proposed vessel designs.

Other objects and advantages of the invention will become apparent as the description proceeds in accordance with the drawing.

In a suitable embodiment, liquid air is housed in a well insulated, jacketed Dewar '1, shown in the figure.

Instead of venting directly to outside the accumulated vapor from the ullage space or vapor space, identified United States Patent 0 ice by 2, liquid is flowed via diptube conduit 3 into the orifice 4 and the heat exchanger, so that venting occurs through the heat exchange. Flow through the orifice 4 is associated with pressure reduction and expansion of the fluid which, as should be obvious, flashes from the liquid to the gaseous state. This in turn provides fluid in exchanger tube 5 of temperature low enough to condense vapor external to the exchange tube in space 2. Such heat exchange condenses vapor in the vapor space 2 and lowers the pressure within the pressure vessel 6. In the illustrated embodiment, and in acordance with conventional practice, fluid may be pressure-driven in liquid form from the container via the line 9 and valve shown at the top right of the figure for use downstream of such valve. Air or other gas moving from the valve 7 (as indicated by the arrow toward the top left of the figure) may simply be vented to atmosphere.

The liquid expanded in said orifice 4 and flowed via said exchange tube 5 for condensation of external vapors at 2, receives heat from condensate, vaporizes at constant pressure which is lower than the tank pressure, and escapes via externally mounted, pilot activated vent valve 7.

Pilot line 8 is in direct communication with vapor space 2, and as such provides accurate control of opening vent valve 7 when pressure in the said vapor space 2 increases above that allowed, and of closing said vent valve 7 when the pressure in said vapor space 2 drops. Since the process of condensing vapors with subsequent lowering pressure in the cryogenic vessel is penformed within the vessel proper and independent of ambient conditions, it provides means of the most efficient operation in the composition control of multicomponent cryogenic fluids and as such provides new type of Dewar design, construction, and operation.

We claim as our invention:

1. In cryogenic storage apparatus that can relieve pressure build-up while maintaining composition consistency of a multicomponent liquid whose components differ in volatility, a cryogenic vessel, an internally located heat exchanger comprising large size tubular conduit means shaped and positioned to establish a heat-exchanging surface within the ul-lage space of the vessel, pressure-reducer orifice means, means for supplying fluid from the vessel interior to said pressure-reducer orifice means, said heat exchanger conduit means leading from said pressure-reducer orifice means and being connected to vent means exterior of the vessel, means for opening and closing said vent means in response to rises and drops of the pressure within the vessel.

2. In cryogenic storage apparatus that can relieve pressure build-up while maintaining composition consistency of a multicomponent liquid whose components differ in volatility, a cryogenic vessel, heat exchanger means within the ullage space of the vessel for absorbing heat from said ullage space, a pressure-reducer device discharging into said heat exchanger means, means for supplying fiuid from the vessel interior to said pressure-reducer device, said heat exchanger means leading from said pressure-reducer device and being connected to vent means exterior of the vessel.

3. In cryogenic storage apparatus that can relieve pressure build-up while maintaining composition consistency of a multicomponent liquid whose components differ in volatility, a cryogenic vessel, heat exchanger means within the u'llage space of the vessel for absorbing heat from said ullage space, a pressure-reducer device discharging into said heat exchanger means, means for supplying fluid from the vessel interior to said pressure-reducer device, said heat exchanger means leading from said pressurereducer device and being connected to vent means exterior of the vessel, means for opening and closing said vent means in response to rises and drops of the pressure Within the vessel.

References Cited by the Examiner UNITED STATES PATENTS Weaver 62-49 Preston 625O Kasbohm et a1 6Q50 X Carney 62-45 

2. IN CRYOGENIC STORAGE APPARATUS THAT CAN RELIEVE PRESSURE BUILD-UP WHILE MAINTAINING COMPOSITION CONSISTENCY OF A MULTICOMPONENT LIQUID WHOSE COMPONENTS DIFFER IN VOLATILITY, A CRYOGENIC VESSEL, HEAT EXCHANGER MEANS WITHIN THE ULLAGE SPACE OF THE VESSEL FOR ABSORBING HEAT FROM SAID ULLAGE SPACE, A PRESSURE-REDUCER DEVICE DISCHARGING INTO SAID HEAT EXCHANGER MEANS, MEANS FOR SUPPLYING FLUID FROM THE VESSEL INTERIOR TO SAID PRESSURE-REDUCER DEVICE, SAID HEAT EXCHANGER MEANS LEADING FROM SAID PRESSURE-REDUCER DEVICE AND BEING CONNECTED TO VENT MEANS EXTERIOR OF THE VESSEL. 